1. Field of the Invention
The invention relates to a light source module. More particularly, the invention relates to a backlight module
2. Description of Related Art
With a quick development of flat panel display technology, liquid crystal displays (LCDs) are widely used in daily life. The LCD has advantages of light weight, small size, low power consumption, thin thickness, etc., so the LCD has gradually replaced a conventional cathode ray tube (CRT).
The LCD includes a liquid crystal panel and a backlight module, wherein the backlight module is disposed at the back of the liquid crystal panel for providing a surface light source required by the liquid crystal panel. The backlight modules may be grouped into direct type backlight modules and side type backlight modules according to positions of light emitting devices thereof. In the side type backlight module, a light guide plate (LGP) is used to guide light emitted from the light emitting device disposed at a side of the LGP to provide the surface light source required by the liquid crystal panel. Moreover, the backlight modules may be further grouped into light emitting diode (LED) backlight modules and cold cathode fluorescent tube backlight modules according to a type of the light emitting device.
In the side type backlight module using the LEDs as the light emitting devices, a plurality of LEDs arranged in a line and spaced from each other are configured beside a light incident surface of the LGP. The LEDs respectively emit a plurality of light beams, and the light beams enter the LGP from the light incident surface. Since the LED has a relatively high directivity, a light emerging angle thereof is limited, so that the LGP may form a bright area at a region near the LED and falling within a range of the light emerging angle, and form a dark area at a region outside of the range of the light emerging angle. The bright area and the dark area may result in uneven surface light source provided by the LGP, and the phenomenon of the uneven surface light source is a so-called hot spot phenomenon. As a power of the LED is continually increased in recent years, a number of the LEDs configured at a side of the light incident surface of the LGP may be relatively less. However, when the number of the LEDs is decreased, the space between two neighbouring LEDs is increased, as a result, the dark area is increased, i.e. the hot spot phenomenon is aggravated, and accordingly the surface light source may be more uneven.
U.S. Pat. No. 7,492,346 and U.S. Pat. No. 7,088,333, U.S. Patent Publication No. 20040183774, and U.S. Patent Publication No. 20090160758 of its patent family disclose a LGP having a light incident portion, a light guiding portion, and a light emerging portion. The light incident portion is located at a corner of the LGP, and the light guiding portion has two bending edges. Taiwan Patent No. I224182 discloses a LGP having a thick side edge. A concave surface of the LGP is a combination of a slope and a curved surface, and the concave surface may guide light emitted by a light emitting device into the LGP. Taiwan Patent No. I249053 discloses a LGP having a light mixing structure and a light emerging portion, wherein the light mixing structure includes a light divergent part and a light convergent part, and an edge of the light divergent part is a straight side. China Patent Publication No. 200510034654 discloses a backlight module including a LGP, a light source, and a reflection mask. The light source is disposed at a corner of the LGP, and the reflection mask is used for guiding the light emitted from the light source into a light incident surface of the LGP.